1. Field of the Disclosure
The disclosure relates to power supply management for mobile communication devices.
2. Introduction
Hybrid energy supplies can only provide peak power for a short time. The hybrid method is to employ a high power/low energy, device such as a capacitor or battery, in parallel with a low power/high energy supply such as a battery or fuel cell. For example, a fuel cell having high series resistance R has its practical output power capability of roughly V squared divided by 10 R, and a small battery or large capacitor having much lower resistance, is provided in parallel.
Multi-mode communications equipment provides data transfer at multiple rates depending on the mode. Multi-mode products allow differing data rates depending on the service type selected. One of the problems to be addressed is the determination of what data mode should be selected. Usually the lowest energy approach uses lower data rates for lower length transmissions and higher data rates for higher length transmissions. This approach makes sense because there is typically a higher amount of processing overhead, and a corresponding amount of overhead energy dissipation, needed for high rate transmissions. For longer transmissions, the energy saved due to lower energy dissipation per transmitted bit exceeds the overhead dissipation.
If the power drain from a high data rate mode exceeds the power supply capability of a high energy supply, one or more high power/low energy supplies may be added, forming a hybrid power supply. However, there is a problem in that the high power/low energy supplies may not be able to sustain a high power transmission for a long period of time. This occurs if the amount of data is large enough that the required energy for its transmission exceeds the energy available from the high power/low energy supply.